Traffic signal controllers support emergency vehicle preemption logic by detecting the light modulated output from an approaching emergency vehicle's mounted emitter. The purpose is to provide a green light for the emergency vehicle as soon as possible or to hold an existing green light. To obtain a green light, existing green lights, including pedestrian intervals, are abbreviated or skipped. After the yellow change interval, a green light is given to the approaching emergency vehicle. The type of signal preemption used for emergency vehicles is a modulated strobe light. A detector at the signal receives light modulated output from a vehicle-mounted emitter.
One significant issue regarding emergency vehicle preemption logic is the potential for fraudulent use or misuse. It can be difficult to capture the misuse of the preemption logic at a traffic signal or tollgate by malicious users. For example, it can be very easy for someone to replicate the emergency strobe lights on their vehicle. Similarly, it can be difficult to capture the misuse of the preemption logic by genuine emergency services professionals (e.g., police officers, emergency medical technicians, fire department personal, and the like). For example, the emergency personnel may activate the strobe light in the emergency vehicle even though the vehicle is not responding to an emergency situation and/or is not allowed to do this legally. Furthermore, there may be other reasons for use of the emergency vehicle preemption logic. For example, currently it is not feasible to quickly “deputize” a citizen and give the vehicle of the citizen the capability to use the emergency vehicle preemption logic. The ability to “deputize” the vehicle of a normal citizen during an emergency situation would be useful in life-saving emergency situations.